'Sin' in the Bible

{Abner became very angry} at the words of Ish-Bosheth, and he said, "[Am] I the head of a dog which [is] for Judah today? Do I not continue to show loyal love with the house of Saul your father, to his brothers, and to his friends? I have not let you fall into the hands of David, yet you have {accused me of sin with this woman} today.

Then David said to Nathan, "I have sinned against Yahweh!" Nathan said to David, "Yahweh has also forgiven your sin; you shall not die.